1. Field of the Invention
The present invention relates to a coupling between the drive shaft of a honing machine and a tool body which supports abrasive elements. The coupling provides universal movement of the tool body on the drive shaft while allowing the passage of the abrasive element adjustment rod from the drive shaft to the adjustment cones. This is accomplished without using the pins typical of the prior art.
2. Brief Description of Related Developments
Machines for boring and finishing cylindrical holes, such as engine cylinder bores, use a tool having abrasive strips mounted on a cylindrical body. As these tools wear, they are generally adjusted radially outward to compensate for the depletion of the abrasive surface. The wear compensating adjustment mechanism forms part of the tool body and comes in many shapes and sizes, for example the tool shown and described in U.S. Pat. No. 4,075,794. These tools consist of a mandrel which connects to the machine spindle at one end and is constructed with an abrasive head at the other. A connecting rod connects to an adjustment mechanism within the abrasive head to bias the abrasive elements radially outward against the work piece. The adjustment can be accomplished automatically as shown in the ""794 patent or manually as shown in the reference Gross, U.S. Pat. No. 2,787,865.
The particular tools, shown in the above referenced patents, are used in honing machines for the construction of bores, such as piston cylinders in automotive engines and similar applications. In the past, such machines have been dedicated to specific tasks in association with particular production runs. With the onset of modern manufacturing concepts such as Just in Time Manufacturing, lean manufacturing, and other inventory reduction methods, there is a need to apply flexible machining systems to the tasks that were previously performed by dedicated machinery. Flexible machine systems generally employ computer numerically controlled (CNC) equipment capable of performing multiple varied operations on multiple workpieces. It is a purpose of this invention to provide a honing tool which facilitates use with CNC machinery.
In order to increase the flexibility of a tool assembly for use in CNC machines, it becomes advantageous to be able to replace the tool body without dismantling the entire tool, which may cause considerable down time. It is a purpose of this invention to facilitate the removal of the tool body from the mandrel so as to allow the replacement of the abrasive elements. A tool having an abrasive head (tool body) which is removable from the mandrel is described in U.S. Pat. No. 5,957,766, which issued on Sep. 28, 1999 to an assignee common to this application. The disclosure of the ""766 patent is incorporated herein by reference.
It is also advantageous to provide a coupling for the tool body to the drive shaft of the machine which allows a universal type of relative movement. Prior art attempts to provide a universal tool mounting typically provided movement about a pair of mutually transverse axes. This was accomplished by constructing matius U-shaped ears on the interface surfaces of the tool body and mandrel. The respective pairs of ears are mated by rotating the tool body ninety degrees from the axially aligned mandrel. Pins are inserted though aligned bores which extend through the ears and the opposing part. Couplings of this type are shown in U.S. Pat. Nos. 4,371,359 and 4,065,881. It is observed that these couplings become complex when provision is made for the passage of the adjustment rod.
It is a purpose of this invention to construct a universal type coupling in which the pins are eliminated, thereby simplifying the manufacture of the tools and mandrels.
It is a purpose of this invention to simplify the coupling of the drive shaft to the tool body while providing a conveniently detachable mechanism which allows for removal of the tool head. It is a purpose of this invention to provide for convenient extension of the adjustment rod through the coupling and for releasably connecting the adjustment rod to the adjustment mechanism. It is another purpose of the invention to strength the coupling by eliminating the pins to provide a stronger structure for the transmission of torque.
A tool is constructed for a CNC machine station to perform a honing operation as part of a flexible machining system. The tool is an assembly of a tool body which holds the abrasive elements, a mandrel which supports the tool body, and a coupling which connects the tool to the CNC machine, as is well known. Commonly the abrasive elements are positioned in axially extending slots positioned circumferentially about the periphery of the tool body. The abrasive elements engage a cone shaped cam that is designed to convert an axial force into a radial force to move the abrasive elements radially. The abrasive elements are spring biased radially inward to provide both extension and retraction of the abrasive elements. The radial force is generally exerted by the motion of a rod extending axially through the mandrel to engage the cam surfaces.
The tool of this invention has a detachable tool body which is connected to the mandrel by means of a universal type coupling. The coupling is designed to allow the passage of the abrasive element adjustment rod.
In the coupling of this invention, the adjacent ends of the mandrel or drive shaft and the tool body are constructed for axial alignment in the assembled position. An axially extending bore is constructed and extends from the drive shaft to tool body to accommodate the passage of an adjustment rod in the assembled position. The mating end of the drive shaft is constructed with U-shaped element having a pair of arms 180 degrees apart extending axially towards the tool body. The inner surfaces of the arms form a partially cylindrical seat. A similar U-shaped element having a pair of similar arms is constructed on the mating interface of the tool body with basically a mirror image profile relative to the drive shaft. The tool body is rotated ninety degrees to mate with the drive shaft. In the assembled position the mated arms define an inner bearing chamber (seat) having dual cylindrical surfaces with transverse axes.
In order to hold the tool body in rotatable engagement with the drive shaft, a barrel is constructed, which is shaped to nest in the seat formed by the mated pair of U-shaped elements. To assemble the tool body on the drive shaft, the barrel is nested within the partial cylindrical seat of the U-shaped element in the drive shaft. The tool body may now be mounted on the drive shaft by displacing the tool body sideways, i.e. transverse to the axis of the tool, and sliding the tool body U-shaped element over the drive shaft U-shaped element. The barrel engages the seat formed by the drive shaft/tool body interface and acts as a bearing which allows dual axes of motion.
The adjustment rod of the abrasive element adjustment mechanism extends from the drive shaft through a bore in the barrel and into the tool body. A transverse slot is constructed in the tool body which connects with the adjustment rod bore. The adjustment rod ends in a spherical portion integral with the rod and connected thereto by means of a neck portion of reduced diameter. The adjustment cone of the adjustment mechanism is constructed with a key shaped slot to allow the engagement of the adjustment rod in the adjustment cone in the same motion that occurs as the tool body is mounted on the drive shaft.
An assembly sleeve is mounted for axial movement on the drive shaft and is slid downward over the coupling to complete the assembly.